Preparation of organo phosphonyl chlorides from organo halides



Patented July 6, 1954 PREPARATION OF ORGANO PHOSPHONYL CHLORIDES FROMORGAN O HALIDES Warren Jensen, Ponca City, Okla., and James 0.

Clayton, Berkeley, Calif., assignors to California Research Corporation,San Francisco, Calif., a

corporation of Delaware No Drawing. Application June 11, 1952, SerialNo. 292,976

4 Claims.

This invention relates to a method of preparing certain phosphonylchlorides and the like by the reaction of organo halides, e. g., alkylchlorides, with phosphorus trichloride in the presence of oxygen.

This application is a continuation-in-part of our copending applicationSerial No. 202,396, filed December 22, 1950.

Phosphonyl chlorides and their derivatives are useful in various arts.For example, certain phosphonyl chloride derivatives (e. g., phosphonicacids and salts and esters thereof) are useful as lubricating oiladditives, fire retardants and textile treating agents; others areuseful in the preparation of wetting agents, emulsifying agents,plasticizers, dispersing agents; and still others are useful asanti-stripping agents for asphalt paving compositions, asphalt pipecoating compositime. etc.

Phosphonyl chlorides having uses in addition to those named above (e.g., useful as insecticides) and being still more diflicult to prepareare those having halogen atoms (e. g., chlorine, atoms) in the moleculeother than the chlorine atoms attached to the phosphorus atom. Theseadditional halogen atoms are attached to carbon atoms.

Readily usable methods are available for the preparation of. phosphonylcompounds wherein the phosphorus atom is connected directly to anaromatic carbon. atom. .l-Iowever', it has been difficult to preparephosphonyl compounds wherein the phosphorus atom is directly connectedto an aliphatic carbon atom. One method which has beenused to producethis latter carbon-to;-

phosphorus linkage consists in heating the hy drocarbon with yellowphosphorus to phosphorize the hydrocarbon, followed by air-blowing toproduce phosphonic acids. This method entails the use of hightemperatures and the consequent dangers of phosphorus vapors. Also, thismethod is highly inefiicient. Various methods have revolved around thereaction of phosphorus trichloride with a hydrocarbon, such methodsrequiring the presence of aluminum chloride or acetic anhydride. Thesemethods are also eX- pensive and inefficient.

V Heretofore, only methods comparable with the above have been availablefor the preparation of phosphonyl compounds having a direct unionbetweena carbon and a phosphorus atom. Now, because of the new reactiondisclosed hereinbelow, these phosphonyl compounds may be prepared on amore extensive scale, which should result in and permit a morewidespread use of these compounds.

It is a primary object of this invention to provide a means of preparingphosphonyl chlorides wherein the phosphorus atom is directly connectedto an aliphatic carbon atom of an organic halide, said phosphonyl halidecontaining at least one carbon-to-halogen bond.

It is another object of this invention to provide a means of convertingan aliphatic carbonto-hydrogen bond of an aliphatic compound containinghalogen atoms bonded to carbon atoms, to an aliphaticcarbon-to-phosphorus bond without the loss of the halogen atom bonded tothe carbon atom.

It is a still further object of this invention to provide a means ofobtaining organo-phosphorus compounds containing at least onecarbon-tohalogen bond and having a carbon-to-phosphorus linkage by amethod using inexpensive organic compounds essentially hydrocarbon instructure and phorphorus trichloride as reactants, which method proceedswithout the necessity of using high temperatures and expensive catalystsand gives high yields to useful carbon-to-phosphorus bonded compounds.

These and further objects of this invention are apparent from thefollowing description and the appended claims.

It has been discovered that organo-phosphonyl chlorides containing acarbon-halogen linkage can be prepared by reacting an organic compoundcontaining a halogen atom attached to a carbon atom with phosphorustrichloride in the presence of air or oxygen, said organic compound.containing at least one aliphatic carbon atom, which aliphatic carbonatom'is bound to at least one hydrogen atom, and said organic compoundbeing free of sulfur and selenium. r

The following chemical equation shows the reaction which takes place:

in where R represents the organic radical of the organic compound, whichorganic compound contains at least one aliphatic carbon atom, and atleast one halogen atom bonded to a carbon atom.

A competing reaction occurs. This competing reaction, which is believedto supply the energy of activation for the above reaction, and to be thestart of a chain reaction, is as follows:

(.2) PC13+ 02 P0013v Thus, the reaction mechanism is wholly differentfrom that of the processes formerly used to pre pare compounds having acarbon-to-phosphorus linkage.

Organic compounds which may be treated according to the process of thisinvention to form the carbon-to-phosphorus bond includehalogencontaining cyclo aliphatic hydrocarbons, wherein the cycloaliphatic hydrocarbons are exemplified by cyclohexane, methylcyclohexane, diethyl cyclohexane, cetyl cyclohexane, tetralin, etc.;halogen-containing aliphatic hydrocarbons, wherein the aliphatichydrocarbons are exemplified by propane, isobutane, pentane,Z-methylpentane, B-methylpentane, hexane, heptane, octane, isooctane,decane, tetradecane, hexadecane, hydrogenated olefin polymers; andhalogen-containing aromatic hydrocarbons substituted by aliphatic orcycloaliphatic radicals, wherein the aromatic hydrocarbons areexemplified by toluene, xylene, hexylbenzene, cetyl benzene,octadecylbenzene, cyclohexylbenzene, etc. Mixtures of halogencontaininghydrocarbons may be similarly reacted, e. g., halogenated gasoline,kerosene, mineral lubricating oil fractions and paraflin wax. Also,halogen-containing substituted hydrocarbons, such as ethers, esters,ketones, etc., and unsaturated hydrocarbons, such as butene-l,isobutene-l, octene-Lisooctene-l, cetene, olefin polymers, etc., may bereacted. Where the substituent or unsaturated linkage is reactive withthe phosphorus trichloride or oxygen, such reaction competes with thedesired reactions leading to the carbon-to-phosphorus linkage, and mayindeed predominate until all the more reactive groups or linkages areconsumed. It is, therefore, preferred to use saturated halogenatedhydrocarbons, or to use unsaturated halogenated hydrocarbons in whichthe unsaturated group is unreactive with phosphorus trichloride andoxygen under the conditions of the reaction.

As used herein, the term halogen includes chlorine, bromine, fluorineand iodine. That is, the organic compound reactants useful according tothe present invention include organic chlorides, fluorides, bromides andiodides.

Organic halides which may be reacted with phosphorus trichloride andoxygen include ethyl chloride, ethyl fluoride, ethyl bromide, n-propylchloride, iscpro-pyl chloride, propyl fluoride, propyl bromide, n-butylchloride, isobutyl chloride, sec.-butyl chloride, tert.-butyl chloride,amyl chloride, dodecyl chloride, cety1 chloride, cetyl bromide,chlorinated petroleum wax, trichloropentane, p-chlorotoluene,p-chlo-rophenyl ethane, cyclohexyl chloride, methyl chloroform,symdichloroethane, 1,1,2-trichloroethane, etc.

The following examples illustrate the phosphonyl compounds which can beprepared according to the process of this invention:

l-chloropropane-2-phosphonyl chloride l-chloropropane-l-phosphonylchloride 1-chloropropane-3-phosphonyl chloride2-chloropropane-l-phosphonyl chloride 2-chloropropane-Z-phosphonylchloride 1chlorobutane2-phosphonyl chloride 1-chlorobutane-3-phosphonylchloride 1-chloro-2-methylpropane-2-phosphonyl chloride .lchlorobutane-ii-phosphonyl chloride2-chloro-2-methylpropane-l-phosph0nyl chloride1-ch1oropentane-2-phosphonyl chloride l-chlorododecane-6-phosphonylchloride l-chlorooctadecane-4-phosphonyl chloride chlorowax phosphonylchloride 1,2-dichloroethane-l-phosphony1 chloride1,1,1-trichloroethane-2-phosphonyl chloride1,1,2-trichloroethane-2-phosph0nyl chloride mixed polychloropentanephosphonyl chloride p-chlorophenylmethane phosphonyl chlorideo-chlorophenyl methane phosphonyl chloridelp-chlorophenylethane-l-phosphonyl chloride1-chlorocyclohexane-2-phosphonyl chloridel-chloroacetopentane-l-phosphonyl chloride2chlorodiethylether-2-phosphonyl chloride1carbomethoxypropane-2-phosphonyl chloride Other phosphonyl derivativesinclude the phosphonic acids prepared by hydrolyzing the abovementionedchlorides, esters of phosphonic acids prepared by reacting the chlorideswith alcohols, phosphonamides prepared by reacting the chlorides withammonia and salts prepared by neutralizing the acids with basicmaterials.

It has been found that certain elements, when present in the organiccompound or in the reaction mixture, inhibit the formation of thecarbonphosphorus bond according to the method of the present invention.For example, when sulfur or selenium is present per se or present as apart of the organic compound, the reaction of the present invention doesnot take place. It has been noted that sulfur and selenium preventoxidation of phosphorus trichloride by oxygen according to the reactionnoted in Equation No. 2 hereinabove. Since this oxidation appears to bethe first step in a chain reaction leading to the formation of aphosphonyl chloride, inhibition of the oxidation process hinders thereaction of the present invention.

When nitro groups (NO2) are present in certain compounds (e. g.p-nitrotoluene), the reaction of this invention is somewhat inhibited.It is believed that this is not due to inhibition of the oxidation ofphosphorus trichloride, but to steric hindrance or resonance effects. Asis normally true in all reactions, it is obvious that where sterichindrances are too strong, or where resonance effects are powerful, thereaction of this invention takes place with difficulty. Such sterichindrances and resonance effects, however, are less felt by aliphaticcarbon atoms which are further removed from the aromatic ring, as forexample, in nitrophenyldecane.

Although phosphorus trifluoride may be used in place of phosphorustrichloride, the latter is much preferred. Air, of course, is thepreferred oxidizing agent to be used in the reaction, but other forms ofgaseous oxygen, such as pure oxygen and commercial oxygen may be used.

The reaction may be carried out in the gaseous or liquid phase, thetemperature varying from elevated temperatures to subzero temperatures.Although the reaction is normally carried out at temperatures well belowthe cracking temperatures of the organic compound reactant, it ispreferred to use temperatures in the range of about -'70 C. to about +75C. particularly from about 0 C. to about +75 C.

The proportions of reactants may ve varied considerably. As the molarratio of phosphorus trichloride to organic compound is increased, theyield of phosphonyl chloride, based on or anic compound charged,increases. Thus, in a specific case where petroleum white oil wasreacted with phosphorus trichloride and oxygen, as the molar ratio ofthe phosphorus trichloride to hydrocarbon was increased from 0.25 to2.0, the yield of phosphonyl chloride (based as hydrocarbon) increasedfrom 715 to 44.5%. molar ratio was increased, the proportion ofphosphor-us trichloride converted to phosphorus oxychloride alsoincreased. Hence, in any given case, "the ratio chosen will depend uponrelative costs However, as the of hydrocarbon and phosphorustrichloride.

The rate of-addition of oxygen does not appear to afiect the yield orpurity, but as the rate of oxygen input is increased, evolution of heatalso increases and more cooling is usually necessary. Itis preferred touse an excess 'of oxygen, but it is also generally beneficial to add theoxygen at "such afrate as will permit maintaining the reactiontemperature-between C. and 75 C.

'I'hQ'DhYSiCEl conditions under which the reaction is carried out willdepend to a considerable degree upon the nature of the reactants. Thus,phosphorus trichloride is relatively volatile (boiling point 76 C.)hence, unless pressure is used, the reaction temperature will be keptbelow 76 0. Where a volatile hydrocarbon reactant, such as ethylchloride, is employed, it may be necessary to use a pressure system forthe reactants. Similarly, if the reaction is made at a temperature abovethat of the boiling point of phosphorus trichloride (76 C.), it may benecessary to'use a pressure system;

Where a normally gaseous organic compound is reacted, the gaseousorganic compound and oxygen may be bubbled through liquid phosphorustrichloride, or the reaction may be accomplished in liquid phase underpressure. Where the organic compound is usually liquid, it may be mixedwith phosphorus trichloride, and oxygen may be bubbled through themixture. Where the organic compound is normally solid, it may be meltedor dissolved in a suitable solvent, such as carbon tetrachloride andtreated as in the case of normally liquid hydrocarbon. Another suitablereaction solvent is benzene.

Methods of recover and treatment of reaction products will likewisedepend in a large degree upon the nature of the materials used, and alsoupon the ends in view. Thus, where the resultant phosphonyl chloride canbe distilled without decomposition, recovery can be efl'ected'byfractional distillation, and, if necessary, vacuum distillation may beused. Unreacted organic compound, phosphorus trichloride (if any), andphosphorus oxychloride will come ofi first, followed by the phosphonylchloride.

Phosphonyl chlorides produced by the reaction of the'present inventionmay be treated with water to produce the corresponding phosphonic acidsby hydrolysis. Where the resulting phosphonic acids are water-soluble,they may be extracted with water. Where the phosphonic acids produced byhydrolysis are water insoluble, the reaction mixture may be extractedwith an aqueous alcoholicsolution of caustic alkali, and the alkalineextract acidified to precipitate the free acids.

The phosphonic acids may be reacted with basic substances to form thecorresponding salts. For example, the phosphonic acids may be reactedwith sodium hydroxide to prepare the sodium salts of the phosphonicacids.

This reaction is extraordinarily simple to carry out. Thus, as describedin detail in the specific examples below, oxygen is bubbled through themixture of the organic compound and phosphorus trichloride. Unreactedorganic compound and phosphorus oxychloride are removed from thereaction mixture by distillation at reduced pressure. The crude organophosphonyl chloride is then distilled off and purified furtherbylredisand advantages of the invention.

Example 1.-Prepaa'at o'n of chlorohezcane phosphonic acid A mixture of42.3 parts by weight of n-hexyl chloride and 241 parts by weight ofphosphorus trichloride was placed in a glass cylinder having 'a'sintered glass bubblin plate at the bottom and fitted with a condenserand a thermometer. Oxygen was bubbled through this mixture at 55 to 60C. until the reaction was complete. The chlorohexane phosphonyl chloridewas hydrolyzed to the chlorohexane phosphonic acid. The 'chlorohexanephosphonic acid reaction mixture was extracted separately with hexane,ethyl ether and benzene. The product recovered vfrom the ether extractcontained 15.8% phosphorus (theor,y=1'5.'5') The pKi and pKz valueswere, respectively, 4.4 and 9.0. The hexane extract prodduct was a dark,viscous oil, the ether extract product was a dark brown viscous oil, andthe benzene extract product was a brown viscous oil.

Example 2.-Preparqtiom of p-chlorphe'ng Z methrme phosphonic acid Amixture of 44.4 parts by weight of p-chlorotoluene and 240 parts byweight of phosphorus trichloride was placed in a glass apparatus, andoxygen was bubbled through this mixture at 55 to 60 C. until thereaction was complete. After the reaction with oxygen, the wholereaction mixture was slowly poured into 2000 parts by weight ofdistilled Water to hydrolyze the phosphonyl chloride. After three hoursof vigorous stirring, the reaction mixture was extracted with hexane,then further extracted with ethyl ether. The ether extract resulted inthe recovery of a light brown solid having a melting point ranging from302 to 310 F. The ether extract product contained 11.59% phosphorus(theory=15.0%)

and 16.4% chlorine (theory=17.l8%). The pKi and pKz values were,respectively, 4.5 and 9.25.

The hexane extract, after removal of the hexane, consisted essentiallyof unreacted p-chlorotoluene.

Example 3. Prepu.ratz'on of trichlorethane phosphonic acid A mixture of44 parts by weight of methyl chloroform and 227 parts by weight ofphosphorus trichloride was placed in a glass apparatus. Oxygen wasbubbled through this mixture at 55 to 60 C. until the reaction wasbelieved to be complete. This reaction mixture was slowly poured intowater, then extracted with ethyl ether. The product recovered from theether extract was a light brown solid containing 7.04% phosphorus(theory=13.4%), and having a pK value of 5.3. The phosphonyl chloridesand. the phosphonic acids prepared according to the methods of thisinvention are useful as intermediates in subsequent preparations.

In the preparation of phosphonyl chlorides according to the presentinvention, phosphorus oxychloride and hydrogen chloride are also formed.Th hydrogen chloride is removed as a gas, after which the unreactedphosphorus trichloride and the phosphorus oxychloride are separated fromthe phosphonyl chloride by distillation. The unreacted phosphorustrichloride and the phosphorus oxychloride may then be heated withcarbon for conversion of the phosphorus oxychloride to phosphorustrichloride according to the wherein the carbon (C) may be obtained ascharcoal, graphite, petroleum, coke, lamp black briquets, bone charcoal,wood charcoal, etc.

The process comprises heating phosphorus oxychloride with carbon attemperatures from about 500 F. to about 900 F., preferably 600 F. to 700F., the temperature depending on the nature of the carbon used. Thegases leaving the reaction zone are conducted to a condenser and gasseparator where the carbon monoxide is separated. The liquid, whichconsists of a mixture of phosphorus trichloride and phosphorusoxychloride, may be recycled to the reaction zone in the furtherproduction of organo-phosphonyl chlorides, or it may be fractionated toproduce an essentially pure phosphorus trichloride.

The use of this process of recovering phosphorus trichloride fromphosphorus oxyohloride reduces the overall cost of the phosphonylchloride, and also eliminates the need for an outlet f or the phosphorusoxychloride.

We claim:

1. The method of producing organo-phosphonyl chlorides, which comprisesreacting an organic compound containing at least one carbon-to-halogenbond and containing two carbon atoms, at least one of which is analiphatic carbon atom bonded to at least one hydrogen atom, withphosphorus trichloride in intimate contact with oxygen at tempearturesbetween C. and C., said halogenated organic compound being free ofsulfur and selenium.

2. The method of claim 1 wherein the reaction mixture is maintained at atemperature between about 0 C. and about +75 C.

3. The method of producing halogenated ethane-phosphonyl chlorides whichcomprises reacting a halogenated ethane containing at least onealiphatic carbon atom bonded to at least one hydrogen atom, withphosphorus trichloride in intimate contact with oxygen, at temperaturesfrom 70 C. to about +75 C. v

4. The method of claim 3 wherein said halogenated ethane is methylchloroform.

References Cited in the file of this patent Jensen et a1. (1) J. A. C.S. vol. '70, p. 3880 (1948).

Jensen et al. (2) J. A. C. S. v01. '71, p. 2384 (1949).

Kosolopoff, Organophosphorus Compounds (1950) pp. 66 and 67.

1. THE METHOD OF PRODUCING ORGANO-PHOSPHONYL CHLORIDES, WHICH COMPRISESREACTING AN ORGANIC COMPOUND CONTAINING AT LEAST ONE CARBON-TO HALOGENBOND AND CONTAINING TWO CARBON ATOMS, AT LEAST ONE OF WHICH IS ANALIPHATIC CARBON ATOM BONDED TO AT LEAST ONE HYDROGEN ATOM, WITHPHOSPHORUS TRICHLORIDE IN INTIMATE CONTACT WITH OXYGEN AT TEMPERATURESBETWEEN -70* C. AND +75* C., SAID HALOGENATED ORGANIC COMPOUND BEINGFREE OF SULFUR AND SELENIUM.